To find X it is a degree value.
All of the angles in this triangle add to give 180 degrees.
So set the sum of every angle = 180
180 = 95 + 3x+4 + 4X-3
To solve this you want x by itself so bring 95 to the other side by subtracting it. Add the 3x and 4X. Add 4 and -3.
85 = 7x + 1
Subtract the 1 to isolate x
84 = 7x
Divide by 7
X = 84/7
To see if it is A, B, C, D plug in the value and see if it adds up to 180